Volume Combustion Modes in Heterogeneous Reaction Systems

Volume combustion synthesis in metal–metal systems (i.e., Ni-Al and Cu-Al) was investigated. Both thermocouple and infrared imaging techniques were used to study the temperature–time history of the process. It was found that in both systems, volume combustion starts at a temperature near the melting point of aluminum. For the Cu-Al mixture, the reaction essentially occurs uniformly along the sample body; whereas, for Ni-Al, propagation of a rapid reaction wave is typically observed. The characteristic temperature gradient of this wave is more than an order of magnitude lower and the velocity of propagation is even higher, as compared with a conventional combustion wave. An explanation of the observed results based on a new class of wave, the so-called virtual combustion wave, is given.